Hey all! I've written up a sort of guide for speedrunning this game on Hard mode. I've divided the different courses into their own sections and provided tips on how to handle every stage with stuff like chaining goals and AI mechanics.
RunRun (Hard):
Rider: This strat is for 26-27sec times. Rider only places 3 pieces. Based on RNG,
- Rare scenario. You receive a 2chain AC. Rider must place a piece in col3/4 so that the result is a 2-high col3/4 (her piece + 1 line of garbage from the 2chain). Then, 2ACs to finish (you may need to power a bit to ensure 5rows are sent on each turn.)
- This one is more common. Rider paces her first piece. Achieve a 4chain AC that send 5lines. Set off the AC, which must send 5 lines too. During this time, Rider must somehow heighten col3/4 by 2.
TaruTaru: Always sets off 2 chains, and only 2 chains (unless forced not to, like getting a big Puyo with a flat board). This means if you ever see him set up a 2 chain, your run... is kinda dead, if he gets the piece to set it off. Because of this, if you can get an early AC you can stop him from doing this in the first place. Early garbage on rare occasion makes him stack up more in the middle for some reason so you can poke it out to finish him in these cases, leading to 22~25sec times, but otherwise setting off your AC chain can finish him easily for a ~30sec time.
Accord: Similar in behaviour to TaruTaru, but usually aims for 2-3 chains, occasionally reaching 4. You can't really rely on getting ACs here but if you do, that's great. If not, you simply need to overpower her first chain (e.g. your 5chain vs her 3chain and then finish her.)
WakuWaku (Hard):
Raffine: This battle goes the same way as Rider's in the RunRun course, except that the first scenario is basically impossible due to All Clear chains no longer being easily AC-able. As such, the battle should go as follows: Raffine paces her first piece. Achieve a 4chain AC that send 5lines - this should be set off using the big (colour-switchable) Puyo. Set off the AC, which must send 5 lines too. During this time, Raffine must somehow heighten col3/4 by 2.
Oshare Bones: Try to go for a 4-chain AC the same way as done in Raffine's battle. Sometimes Oshare heightens the middle columns a lot, so in these cases you can break the AC to make it send less (in order to save time), like activating the Stairs AC from the right to make it only a 3 chain. He strictly goes for 2 chains (and so avoids 1 chains), similar to TaruTaru, but also never rotates, so he should never be able to set anything off during a run. One difference is that going for an AC of a different length (3 or 5) is not too punishable here as any garbage helps, due to the fact that the AI actually places pieces (in Raffine's stage you are optimising her number of pieces placed to make up for her auto-drop speed). As such, feel free to take 2-3 chain ACs or 4 chain ACs before using the big Puyo. Anything larger than that, though, isn't necessary.
Rider: Similar to Oshare, she only sets off 2 chains, though sometimes it happens to be a 3. As she is faster, you'll need to make sure she never has one that is ready to set off. You can use the same technique as in the previous stage (4chain AC if possible, but any AC works).
Dongurigaeru: Frogstacking...! OK, so this is where you start getting 4 colours. Going for an All Clear does not work 100% of the time, but go for it if you can. If not, I recommend a 5 chain. BEWARE! Dongurigaeru is the start of all AIs using the "stalling" mechanic - that is, they will take ANY 1 chain available to them while they have garbage above them or if they're high up. As such, you'll want to send your chain while he doesn't have anything to use (just finished the frogstack and has no links) or after he sets off something from his frogstack.
Klug: He's a bit of an oddball. He aims for 3 chains, but sometimes doesn't do anything for ages. Sometimes if you strike him out before he sends anything (with a 4 chain or so) it'll be enough, but if he looks like he has a chain available, go for a 5. If you decide to go for the latter, remember: the AIs have started to stall. You want to counter his rather than attack first, because if you attack first while he has many resources, he may simply opt to 1-chain his way to Fever.
Frankensteins: They go for 3 chains as well. Since they build faster, you'll only want to take ACs if they are early enough. If not, hit them with a good 4-5 while they don't have enough to set off or after their chain resolves. Notably, this is where the AI begins to utilise the "panic" and "relax" mechanics. The former means that they will play faster while high up, which means they have a higher chance of digging down or forming multiple links to 1-chain with. The latter means that when you are under attack (have garbage above you), they will slow down. With regards to "panic mode", make sure you follow up quickly after your first attack. If you don't feel you will be ready to follow-up (or otherwise don't have enough to take them out completely with your attack), it's actually safer to avoid attacking in the first place. This is also why countering their first chain is a strong move - they'll have used their resources and also will not try to place more pieces quickly while your chain is being set off, leaving them vulnerable.
Arle: This is where you'll start to get 5 colours. Arle will try to go for 4 chains. Remember your attack power is lower now, so you'll need to aim for more - a solid 5 chain or even a 6 should do the job. As always, an AC is welcome but specifically searching for them will not yield results very often. The nice thing is that Arle's dropset is purely pairs, so she often has less resources to work with.
Popoi: This stage is pretty much the same as Arle's, except with a more aggressive "panic" mode, so be really careful about sending him garbage. If you spot him in a position where he can't send off much, that's a good time to strike. If not, simply overpower his chain to counter and win.
HaraHara (Hard):
Onion Pixy: Right off the bat, the AI will use the "stalling" mechanic - that is, they will take ANY 1 chain available to them while they have garbage above them or if they're high up. Additionally, the AI will utilise the "panic" and "relax" mechanics. The former means that they will play faster while high up, which means they have a higher chance of digging down or forming multiple links to 1-chain with. The latter means that when you are under attack (have garbage above you), they will slow down. This isn't too important for the first stage, but it is key to know that it's present for the entire run. In general, Onion Pixy goes for 3 chains, which gives you a good amount of time to set up something of your own. He also doesn't rotate. As such, you can use the same strategy as in the early WakuWaku stages - try to go for a an early AC. Sometimes Onion Pixy heightens the middle columns a lot, so in these cases you can break the AC to make it send less (in order to save time), like activating the Stairs AC from the right to make it only a 3 chain.
Klug: He goes for 3 chains just like Onion Pixy, but can of course rotate and has to deal with 4 colours (it's not much of a hindrance to his chaining but can stop him from stalling some of the time). An early AC here is the key, just like in the previous stage. Be sure to follow up on your attacks early, since - remember - the AI will activate "panic" mode when being sent attacks and while high up, leading to drawn-out battles. Try not to let this happen.
Prince of ocean: This is where you start receiving 4 colours. Prince of ocean goes for 4 chains. An AC is good if you can get one, but if not, you'll need a strong 5 or 6 to counter his chain and take him out.
TaruTaru: He goes for 4 chains. ACs from here can be a bit risky, but again, if it's solid, then it should work out. Again, a strong 5 or a 6 is what you'll need.
Yu: OK I know what I said before, but an early AC is basically your only solution for a fast stage. This is because Yu has 3 colours and Harpy-stacks - that is, she fills the columns on both sides of the board. As a result... she basically has infinite stalling potential and will get into Fever with ease. Maybe even twice. An early AC stops her from building up resources and the AC chain itself should be able to finish her. Otherwise, say goodbye to your run.
Hohow Bird: 5 colours time! He'll go for a 4 chain but a higher chain isn't super uncommon. Once again, a solid 5 or a 6 is what you're looking for. Fun fact, from here, if you get the AIs into panic mode, they'll play at full speed! Yep, Hohow and Miss Accord will play like Carbuncle if they're in danger. Be really careful about when you send attacks.
Ms Accord: Haha. This is where it gets really rough. She'll go for 5 chains but will sometimes hit a 6. You're gonna have to smash out a 6 chain or better to counter her chain and take her out.
Carbuncle/Popoi: The final battle! You should land on Carbuncle if you've had a good run but otherwise you'll get Popoi. And by that, I don't just mean continues! If you got here with no continues but also got more than 4 Fevers during the run, you'll still get Popoi. Uh... I guess if you had a really awkward run with no continues and more than 12 Fevers you'd still get Carbuncle, but. That's awkward. Anyway! Strats. Regardless of who you get, they'll actually play at full speed straight away - they will only slow down when in "calm mode" (as a reminder, this is when you have garbage above you). They'll aim for a 5 chain, but may reach a 6. You'll need a 6 or even a 7 to be safe on clearing. Good luck!!!
An Additional Note (for unoptimised runs): One other AI quirk that only comes up in Fever is "survival" mode. This is present from Frankensteins onwards in WakuWaku and for the whole course in HaraHara. What this does is that whenever the AI has active garbage above them, they'll clear with anything they have to avoid receiving garbage - this means that they may set off the Fever chain in a sub-optimal matter, perhaps simply even clearing a 1 chain. This is usually in their best interests, but you can exploit this - if they happen to get Fever (I'd say this is most common with Yu), you can simply send a 1 chain as they enter (to disrupt their first chain) or at the end of their Fever chain (to disrupt their next chain) to have them activate survival mode. It doesn't always work, as the AI does go for the proper clear of the Fever chain if they are given the colour, but in the case that they don't, they'll be hindered. A fun fact on this tip: this is also used in PvP Fever battles! Once margin time kicks in hard, players will start 1-chaining each other (which can send a rock or more!) whenever the other finishes a Fever chain in the hopes that their opponent won't get the piece they need to set off their next chain. The opponent needs to react the same way the AI does here, by setting anything off to keep themself alive. If they have no options, it's over.
